The present invention relates to a defrost control method and apparatus of a refrigerator.
A refrigerator generally includes a cabinet in which food storage compartments such as a refrigerating compartment and a freezing compartment are formed, a cooling system for cooling food stored in the food storage compartments and doors for opening and closing the refrigerating and freezing compartments. The cooling system includes a compressor for compressing a refrigerant, a condenser for condensing the refrigerant from the compressor and an evaporator for evaporating the refrigerant from the condenser to generate a cool air. The evaporator generates the cool air by cooing the ambient air by evaporation latent heat of the refrigerant flowing inside the evaporator. The thus-generated cool air is supplied to the refrigerant and freezing compartments by a blowing fan.
In such a refrigerator, moisture is condensed and freezed on the surface of the evaporator by the difference of relative humidities between the surface of the evaporator having a relatively low temperature and the ambient air having a relatively high temperature, to thereby generator frost. The frost formed on the surface of the evaporator hinders thermal exchange of the evaporator, thereby lowering the cooling efficiency and increasing power consumption. In order to overcome the problem, a refrigerator having a defrosting heater adjacent to an evaporate to remove frost formed on the surface of the evaporator has been developed recently.
The amount of frost formed on the surface of the evaporator is proportional to the operation time of the compressor and increases according as inflow of ambient air into the refrigerator increases by opening of the doors. That is, the amount of frost depends on the operation time of the compressor, the number and time of the door opening and the temperature of ambient air. Considering these factors, various defrost time determining methods are proposed.
A defrost time determining method disclosed in U.S. Pat. No. 4,297,852 determines as a defrost time when the sum of the operation time of a compressor is above a predetermined value and then the sum of the door opening time reaches a reference value. However, this method does not consider the affect of the temperature of ambient air.
Another defrost time determining apparatus disclosed in U.S. Pat. No. 5,564,286 includes as elements thereof a compressor operation timer, a door opening counter, a door opening timer and an outside temperature sensor and determines a defrost time according to fuzzy logic reasoning using values measured by the elements. Here, after compressor operation time passes a predetermined time, the defrost time is judged based on the door opening number and the outside temperature. On the other hand, the defrost operation is independently performed when the sum of the door opening time is above a reference value without consideration of other operating conditions. However, this apparatus has a drawback that the process of determining the defrost time is relatively complicated.